The field of this invention is that of pressure-responsive switches and the invention relates more particularly to pressure responsive switches which are adapted to be manufactured at low cost for use in various applications where high performance characteristics are required.
Pressure responsive switches conventionally incorporate a diaphragm which is exposed to fluid pressures in a zone to be monitored so that the diaphragm moves in response to applied fluid pressures. The diaphragm is typically arranged to actuate an electrical switch or the like when an applied fluid pressure reaches a selected level. In many applications, such switches primarily serve a safety function for discontinuing operation of a compressor motor or the like if fluid pressure in the zone exceeds a safe level. Accordingly, the switches have a long service life but are required to undergo only a limited number of operating cycles during that service life. In such conventional applications the pressure switches also tend to be subjected to relatively low operating pressure levels. Accordingly, the performance requirements for such switches are relatively easy to meet. More recently however, some pressure responsive switches have been used in applications where they are intended to perform repetitive control functions rather than protective functions and are therefore required to perform accurately over a very large number of operating cycles. In some of those new switch applications, the switches are subjected to very high operating pressures in normal operation of the switches and have to be capable of withstanding even much greater pressures under certain over pressure conditions without loss of accuracy or device function. Pressure switches adapted to meet these more stringent performance requirements have tended to be much more expensive to manufacture and it has typically been found that switches as manufactured are subjected to relatively high rejection rates when tested for meeting desired performance specifications.